Beta-mercaptopropionitrile and processes for their preparation



Patented Mar. 3, 1.953

BETA-MERCAPI'OPROPIONITRILE PROCES SE S FOR THEIR PREPARATION i WillieeW. Crouch and Robertrr. Workman, Bar-- tlesville, Okla.-, assignors etc Phillips Petroleum Company, ,a corporation of Delaware NdDrawing; Original application November 28; 1949;" Serial No. 129,866. Divided and this ap plication Niivember 19, 1951; Serial N;-25Z7,1Bfif 7 Claims... I (Chim -465.11.

This invention relates. to g novel" crganic'sulfur and nitrogen containing "compounds, namely, 2-

cyanoethyl thiolacetate and beta-mercaptopropionitrile. In one of its aspects, this invention relates toia process ior the production of'2 cyano ethyl .thiolacetate by reacting thioacetic acid and acryloniti'ile in the presence of a basic catalyst. Infxanother of its :aspects, this invention relates to: a process for hydrolyz'ing 2 cyanoethyl' thiolacetat'e' to" produce betamercaptopropionitrile.

In yet another of its aspects, this invention relates.

to a process for: reactmg 'th'ioaceticacid with acryl'onitrile' in" the" presence of a catalyst com-.

prising 'eitlr'er' a'quatern ary ammonium compound oria tert-butyl hydrop'eroxide:

This application is-a divisionof our copen'dingbervulcanization, modifier in emulsion polymerization recipes forming synthetic rubber, lubricatingoil additives, medicine, ore flotation, dye prodiiction, etc:

According to. this invention, therehave been prepared novel Lorganic sulfur. and nitrogen containing compounds, namely, Z-cyanoethyl thi'olacetate and beta-mercaptopropionitrile. Still accordingtothis invention, there has been set forth;

asprocess for-the production of 2-oyanoethy1 thiolacetatelbythe reaction of thioacetic acidand acrylonitrile in the presence of a basiccatalyst withcutany substantial; concomitant hydrolysis of, the nitrile radical and without undesirable polymerization of the acrylonitrile reactant.

Still further accordingto this invention, it has been found thatZ-cyanoethyl thiolacetate can be hydrolyzed to beta-mereaptopropionitrile. in excellent yields without any" substantial decomposition of the nitrileradical to a corresponding'acid.

Thus, according to this" invention, thioacetic acidzandacrylonitrile 'are reacted to yield a novel compound, 2-cyanoethyl thiolacetate. The reaction. can-bezillustrated bythe following equation:

. u crn=cncn CHaCOSH" omc-s-cmomon momma thicacetic and":

z-cyanocthyithiolacetate Thebest yields of the thiolacetate producthave been obtained when approximately equi-molar proportions of theereactants are employed. However, such proportion ofthereactants is notnecessary and if other proportions areemployed, it is preferable to use a greater molar'quantity Ofgth thioacetic acid than of the acrylonitrile. The reaction is one of addition and is highly exothermic in nature. Accordingly, the rate of "reaction must be carefully controlled to avoid excessively high reaction temperatures which resulttin polymerization of the acrylonitrile to form acrylic polymers and resins. Usually one of the reactants is added to the other at a slow rate so that sufficient time is allowedior dissipation'or :removal of the exothermic heat of reaction either by radiation or by'suitable cooling coils. Upon completion of the reaction, the 2-cyanoethy1 thiolacetate product can be readily separated from unreacted materials by simple fractional distillation.

As stated, the temperature of thethioacetic acid-acrylonitrile addition reaction is maintained Within a range sufiiciently low to prevent any substantial polymerization of the acrylonitrile and to prevent decomposition'of the thiolacetate product. As a general rule, a temperature within the range of 10 to 150 0., preferably from 25 to 95 0., still morepreferably from 30 to C., is satisfactory. The exact temperature to be employed depends on the efficiency of the catalyst employed, the purity of the reactants and upon the desired overall yield of product. In any event, the optimum temperature can be determined by mere routine. test.

The-pressure to be employed in the addition reactionis not critical and can range from substantially atmospheric to 10 atmospheres or even higher. A pressure sufficiently high to. maintain-liquidphase reaction conditions is preferred.

In accomplishing the thioacetic acid-acrylonitrile reaction, it has been ioundto be highly advantageous to employ certain basic catalysts as reaction promoters and directors. The preferred catalyst isya quaternary ammonium compound, designated by the general formula" It has a very disagreeable odor. Other properties of the compound are:

Boiling point at 3mm. Hg. absolute pressure C 9 I Density, d l 1212 Refractive index, n l. 4912 tolyl, etc. A particularly preferred catalyst is trimethylbenzyl ammonium hydroxide although other catalysts such as dimethylethylbenzyl ammonium hydroxide, methyldiethylbenzyl ammonium hydroxide, etc. are satisfactory. Another catalyst which has been found to be effective is tert-butyl hydroperoxide although it is usually preferable to employ a quaternary ammonium compound. As a general rule, it has been found necessary to employ only very smal1 concentrations of the selected catalyst in order to effectively promote and direct the addition of the reactants. Thus, from about 0.1 to 5, preferably from 0.5 to 2, parts by weight of the catalyst per 100 parts by weight of the thioacetic acid reactant are employed. The use of an insufiicient concentration of catalyst results in the formation of polymers of the acrylonitrile reactant with a resultant decrease in overal1 eiiiciency of the process and plugging of the reaction equipment with the polymers.

The Z-cyanoethyl thiolacetate produced in accordance with the process of this invention is a clear, pale yellow liquid at room temperature.

As stated, this compound is valuable as an inter-.

mediate in organic syntheses inasmuch as it exhibits reactivity not only through the divalent sulfur but also through the nitrile and the carbonyl groups. Hence, many derivatives can be prepared from this compound by utilizing reactions characteristic of these three reactive groups.

In accordance with this invention, the novel 2-cyanoethyl thiolacetate prepared by the abovedescribed process can be hydrolyzed to yield another novel compound, beta-mercaptopropionitrile. Thus, the hydrolysis reaction is as follows:

CHaC-S-CH2CH2CN HOH 2-cyanocthyl thiolacetate U HSCHzCHzCN CHaC OH beta-mercapto acetic acid propionitrilc The hydrolysis reaction is preferably performed in the presence of a basic material, e. g. an alkali metal hydroxide such as sodium or potassium hydroxide, dissolved in sufficient water to yield a weight of a 5 to 20, preferably a to weight per cent solution of an alkali per part of ester to be hydrolyzed, within a period of time as short as 15 minutes. The alkali which is employed can I be sodium, potassium, or lithium hydroxide, etc.

After the hydrolysis reaction, the beta-mercaptopropionitrile product is separated from the remaining aqueous solution of basic material by acidifying the solution with an inorganic acid such as sulfuric, hydrochloric, etc., to a pH between 4.5 and 6.0. The acidified solution then separates into an oily phase and an aqueous phase. The nitrile can be recovered and purified in any suitable manner. For example the water phase can be extracted with ether to extract the last traces of oil. The beta-mercaptopropionitrile can then be readily recovered from the combined oil and ether extract phases as a substantially pure product by simple distillation. If desired the ether may be separated from the ether extract phase and the oil combined with the separated oil phase. The product is a water-white liquid having a disagreeable odor as well as the following properties Boiling Point at 15 mm. H g., absolute pressure 0; 75 Density, 6% 1.0696 Refractive index n 1.4877

Example I Two hundred grams of thioacetic acid was slowly added to 142 grams to acrylonitrile' containing one milliliter of trimethylbenzyl ammonium hydroxide catalyst. The mixture was stirred continuously and was initially warmed to a temperature of 38 C. The acid was added over a period of two hours. The exothermic heat of reaction maintained the temperature between 38 C. and 105 C. during this period.

Distillation of the reaction product yielded 300.5 grams of 2-cyanoethyl thiolacetate. This represents a yield of distilled product of 88.6 per cent of theory based on thioacetic acid.

Example II Hydrolysis of a 77.3 gram sample of the 2- cyanoethyl thiolacetate produced in Example I was effected with grams of a 12 weight per cent aqueous sodium hydroxide solution. The mixture was stirred during the hydrolysis and was maintained below 32 C. (but above 0 C.) by means of an ice bath. Within 15 minutes the ester was completely dissolved in the caustic solution. The mixture was then acidified to pH 5 and an oily layer separated from the water phase. Two milliliter portions of ether were used to extract last traces of oil from the water phase. The oil phase and ether extract were combined and distilled to yield 37 grams of beta-mercaptopropionitrile. This is equivalent to 71 per cent of theoretica1 conversion based on the amount of 2- cyanoethyl thiolacetate used.

Example III Five-tenths milliliter of trimethylbenzyl ammomum hydroxide catalyst was admixed "with 51.4 grams of acrylonitrile. Then 28.2 grams of thioacetic acid was quickly added with stirring to the acrylonitrile-catalyst mixture. The temperature rose rapidly to 74 C. An additional 4.6 grams of thioacetic acid was added at a rate such that the temperature in the reaction vessel was maintained at 65 to 71 C. About one hour was required to add the additional 46 grams of acid. The reaction mixture was then stirred for an additional one hour period.

The product was distilled and 108 grams of 2- cyanoethyl thiolacetate was recovered. This represents an actual yield of pure product amounting to 86.3 per cent of the theoretical yield based on acrylonitrile.

Example IV Thirty-three point six grams of acrylonitrile containing one weight per cent tert-butyl hydroperoxide catalyst was added dropwise to 39 grams H of thioacetic acid. The reaction mixture was heated to 43 to 49 C. and stirred throughout the run. About two hours were required to add the acrylonitrile.

The product was distilled and 19 grams of 2- cyanoethyl thiolacetate Was recovered. This represents an actual yield of pure product amounting to 28.7 per cent of the theoretical yield based on thioacetic acid.

Reasonable variation and modification are pos- We claim:

1. Beta-mercaptopropionitrile.

2. A process for producing beta-mercaptopropionitrile comprising contacting Z-cyanoethyl thiolacetate with an aqueous solution of an alkali metal hydroxide.

3. A process for producing beta-mercaptopropionitrile comprising contacting Z-cyanoethyl thiolacetate with an aqueous solution of an alkali metal hydroxide at a temperature between and C.

4. The process of claim 2 wherein the alkali metal hydroxide is sodium hydroxide.

5. A process for producing beta-mercaptopropionitrile comprising reacting thioacetic acid with acrylonitrile in the presence of a catalyst to form 2-cyanoethyl thiolacetate, hydrolyzing the said 2-cyanoethyl thiolacetate with a cold aqueous solution of an alkali metal hydroxide to form the desired beta-mercaptopropionitrile.

6. The process of claim 5 wherein the said catalyst is trimethylbenzyl ammonium hydroxide.

7. A process for producing beta-mercaptopropionitrile comprising reacting acrylonitrile with thioacetic acid in the presence of small amounts of trimethylbenzyl ammonium hydroxide at a temperature between 38 and C., recovering the thus produced Z-cyanoethyl thiolacetate, hydrolyzing the said Z-cyanoethyl thiolacetate with an aqueous solution of sodium hydroxide at a temperature between 0 and 32 C., acidifying the thus resulting mixture of beta-mercaptopropionitrile and aqueous sodium hydroxide, and separating the beta-mercaptopropionitri1e from the acidified solution by ether extraction and distillation.

WILLIE W. CROUCH. ROBERT T. WERKMAN.

No references cited. 

1. BETA-MERCAPTOPROPIONITRILE. 